Radio frequencies are allocated by the Federal Communication Commission to particular uses. Allocations of the radio spectrum for radio amateurs has present a problem in that the width of any given band is too wide for a single antenna. Antennas that are available to radio amateur operators can tune only a portion of any given band. When an operator installs an antenna, he has to decide in which portion of a given band that he wishes to operate. The antenna is then tuned to that portion of the band, and the operator can only efficiently operate in that portion of the band.
If the operator wishes to operate in a different portion of a given band of frequencies, the antenna has to be taken down and returned for that different portion of the band. Since antennas are mounted high in the air on a antenna mast, it is not practical to retune the antenna.
An alternative to retuning the antenna is to use an antenna tuner. This method of retuning only hides the effects of a mistuned antenna from the operators transmitter, is not efficient and does not solve the basic problem. Antenna tuners use variable capacitors and coils. Example of antenna tuners are found in U.S. Pat. Nos. 3,653,053 and 2,976,532. U.S. Pat. No. 2,976,532 uses capacitive tuning.
Telescoping antenna construction can be used to tune antenna, but this does not eliminated the need to remove an antenna from its mount to retune by sliding the telescoping elements. U.S. Pat. No. 4,620,194, uses telescoping elements for all of the elements. The sliding of telescoping elements provides an inductive change, retuning the antenna. This antenna also has to be accessed to change the tuning, and clamps loosened to retune the sliding elements.